A “coaxial-stripline converter” has been proposed to transfer a high-frequency signal to a signal line configuring a stripline formed in a laminated substrate. Further, a technique for improving long-term reliability with respect to a temperature change by reducing an aspect ratio of a via used in the “coaxial-stripline converter” has been proposed. In the technique, vias conducting in a stacking direction (the up-down direction) are provided for each of dielectric substrates present between a connected coaxial connector and the stripline. Further, these vias are disposed side by side in the stacking direction. Using a plurality of vias enable an aspect ratio of the respective vias to decrease, and capacitive coupling of the vias opposed to each other enable transfer from the coaxial connector to the signal line.
It has been found that an antenna characteristic of a product which was manufactured by the proposed technique tends to fluctuate. There are many antennas have a specification according to each use of the antennas for a transmission characteristic. Therefore, there is a demand for a technique for reducing fluctuation with respect to the transmission characteristic.